This invention relates to a method for preparation of single chain antibodies, and is of particular applicability to preparation of single chain Fv antibody fragments (scFv) where the antigen to which the antibody binds is difficult to purify.
ScFv are antibody constructs comprising the variable regions of the heavy and light chains of an antibody as a single chain Fv fragment. ScFv technology utilizes molecular biology methods to reduce antibodies to the minimal-required-unit of heavy and light chain variable regions tethered by a peptide linker which can be designed with versatile side chains for radioconjugation.
Procedures for making scFv are known in the art. These procedures generally involve amplification of gene regions encoding the variable regions of the antibodies, assembly of an scFv genetic sequence and expression of the scFv genetic sequence in host cells. The host cells are screened using a target antigen to identify those cells which bind to the antigen, ands thus which express a functional scFv of the desired specificity. While this procedure works well in many cases, it requires the isolation of the antigen for use as a screening tool. In some cases, however, particularly in the case of membrane bound receptor molecules, this isolation may be difficult, or the conformation of the isolated antigen may be so different that it fails to present the same epitopes for binding. In these cases, the conventional techniques for development of an scFv are either unworkable or very difficult.